Armstrong Air Conditioning 4HP14 Installatie- en opstartinstructies - Pagina 7
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Pagina afdrukkenSYSTEM OPERATION
The outdoor unit and indoor blower cycle on demand
from the room thermostat. When the thermostat blower
switch is in the ON position, the indoor blower operates
continuously.
Filter Drier
The outdoor unit is equipped with a bi-flow filter drier. If
replacement is necessary, order new dryer according to the
service parts manual.
Emergency Heat Function (Room Thermostat)
An emergency heat function is designed into some room
thermostats. This feature is applicable when isolation of
outdoor unit is required or when auxiliary electric heat is
staged by outdoor thermostats. When the room thermostat
is placed in the emergency heat position, the outdoor unit
control circuit is isolated from power and field-provided relays
bypass the outdoor thermostats. An amber indicating light
simultaneously comes on to remind the homeowner that he
is operating in the emergency heat mode.
Emergency heat is usually used during an outdoor unit
shutdown, but it should also be used following a power
outage. If power has been off for over an hour and the
outdoor temperature is below 50°F (10°C). System should
be left in the emergency heat mode at least six hours to
allow the crankcase heater sufficient time to prevent
compressor slugging. This applies only to systems with
crank case heaters.
Defrost System Time-Temp
The defrost system includes two (2) components: a
defrost thermostat and a defrost control.
Defrost Thermostat
The defrost thermostat is located on the outdoor coil of
most models and on the liquid line between the check/
expansion valve and the distributor on R-4110A TXV
equipped models. When defrost thermostat senses 29°F
(42 on R-410A TXV's) or cooler, the thermostat contacts
close and send a signal to the defrost control board to start
the defrost timing. It also terminates defrost when the liquid
line warms up to 60°F.
Defrost Control
The defrost control board includes the combined
functions of a time/temperature defrost control, defrost relay,
diagnostic LEDs and terminal strip for field wiring
connections.
506318-01
The control provides automatic switching from normal
heating operation to defrost mode and back. During
compressor cycle, the control accumulates compressor run
times at 30-, 60-, or 90-minute field-adjustable intervals. If
the defrost thermostat is closed when the selected
compressor run time interval ends (call for defrost), the
defrost relay is energized and defrost begins. The factory
setting is 60 minutes. However, if frost accumulation is easily
cleared, the optimum efficiency setting is 90 minutes.
Outdoor Unit Defrost Control Board
Defrost Control Timing Pins
Each timing pin selection provides a different
accumulated compressor run time period for one defrost
cycle. This time period must occur before a defrost cycle is
initiated. The defrost interval can be adjusted to 30 (/T1),
60 (T2), or 90 (T3) minutes. The defrost timing jumper is
factory-installed to provided a 90-minute defrost interval. If
the timing selector jumper is not in place the control defaults
to a 90-minute defrost interval. The maximum defrost period
is 14 minutes and cannot be adjusted.
A TEST option is provided for troubleshooting. The TEST
mode may be started any time the unit is in the heating
mode and the defrost thermostat is closed or jumpered.
If the jumper is in the TEST position at power-up, the control
will ignore the test pins. When the jumper is placed across
the TEST pins for 2 seconds, the control will enter the defrost
mode. If the jumper is removed before an additional 5
second period has elapsed (7 seconds total), the unit will
remain in defrost mode until the defrost thermostat opens
or 14 minutes have passed. If the jumper is not removed
until after the additional 5 second period has elapsed, the
defrost will terminate and the test option will not function
again until the jumper is removed and re-applied.
Issue 0946
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